Artificial leather and its manufacturing method

Abstract

To provide a recyclable artificial leather having a set of good feeling, high abrasion resistance, and high-class feeling appearance.SOLUTION: An artificial leather at least includes a surface fiber layer constituting a first surface, where (1) the surface fiber layer is composed of at least one main fiber, and a thermoplastic resin having a melting point lower than a melting point of the main fiber by 20°C or more, (2) the fineness of the main fiber is 0.01 dtex or more and 0.5 dtex or less, (3) at least one part of the thermoplastic resin bonds between the main fibers, (4) the number average volume of the thermoplastic resin in the surface fiber layer when measuring the first surface by X-ray CT is 5,000 μm3 or larger and 14,000 μm3 or smaller, and (5) the volume number density of the thermoplastic resin in the first surface fiber layer is 1.1×1012 / m3 or more and 3.0×1012 / m3 or less.SELECTED DRAWING: Figure 9

Description

[Technical Field]

[0001] The present invention relates to an artificial leather and a method for producing the same. [Background technology]

[0002] Artificial leather has been widely accepted in the market as an alternative to natural leather, and is widely used as a highly functional design material because it is available in a wide variety of product styles, including grain and suede finishes, and can be dyed to produce a wide range of colors not available in natural leather. In particular, suede-finish artificial leather with a brushed outer surface is suitable for use in fields such as clothing, shoes, bags, furniture, and seat coverings and interior materials for automobiles, railway vehicles, aircraft, and ships. In these fields, there is a demand for a combination of good appearance quality, a supple feel, and resistance to physical loads, such as abrasion resistance during long-term use.

[0003] According to the definition of JIS-6601, artificial leathers are classified by appearance into "smooth," which has a grain-like appearance of leather, and "napped," which has the appearance of leather such as nubuck, suede, or velour. The artificial leather of this embodiment relates to one classified as "napped" (i.e., a brushed artificial leather with a brushed appearance). The brushed appearance can be achieved by buffing (raising) the outer surface (also referred to as the front surface) of the main fiber layer with sandpaper or the like. In this specification, the outer surface of the artificial leather, the outer surface of the main fiber layer, the outer surface of the fiber sheet, and the outer surface of the laminate sheet refer to the surfaces exposed to the outside when used as artificial leather (for example, the surface that comes into contact with the human body in the case of a chair). In one embodiment, in the case of brushed artificial leather, the outer surface of the main fiber layer is brushed or raised by buffing or the like.

[0004] The mainstream material for artificial leather is a nonwoven fabric structure made by entangling ultrafine fibers made of materials such as polyethylene terephthalate or nylon, and is impregnated with and attached to a polymeric elastomer resin such as polyurethane. If the fibers are simply left physically entangled by needle punching or hydroentangling without being impregnated with a polymeric elastomer resin, the resulting leather will have problems such as insufficient abrasion resistance during actual use, lacking the supple feel of artificial leather, and frequent shedding of threads during the dyeing process, which can lead to manufacturing defects.

[0005] Therefore, in the manufacturing process of artificial leather, a technique of adding a polymeric elastomer such as polyurethane to impart a good texture and abrasion resistance is widely used. For example, artificial leathers impregnated with polyurethane are commercially available under names such as Lamous®, Ecsaine®, and Alcantara®. However, polymeric elastomers such as polyurethane have a high tendency to bleed out dyes, and unless sufficient reduction washing treatment is used, they can suffer from problems such as poor washfastness, UV resistance, and susceptibility to deterioration over time, resulting in color change and degradation over time. In addition, because they cannot be decomposed under the reaction conditions that cause polyester depolymerization, they cannot be recycled when combined with polyester fibers, the most widely used base fiber in artificial leather.

[0006] The following Patent Document 1 discloses an example of using polyurethane with a porous structure as a binder for artificial leather. While this method can achieve good quality at the beginning of production, it has the disadvantage that the polyurethane deteriorates over long-term use, resulting in insufficient abrasion resistance. In addition, the material composition is a composite system of different chemical materials, namely polyester fiber and polyurethane binder, and cannot be a single material composition. Therefore, in order to adapt this to existing recycling processes such as chemical recycling and material recycling, a new removal process technology for separating the polyester and polyurethane must be developed, which creates the problem of making recycling difficult.

[0007] In addition to impregnating and adhering a polymeric elastomer such as polyurethane, a method has been investigated in the past to obtain a binder effect for imparting strength to artificial leather. This involves mixing heat-fusible fibers into the nonwoven fabric for artificial leather during its production and then melting the fibers to bond the main fibers together. For example, in the examples of Patent Document 2 listed below, thick, sheath-core heat-fusible fibers are used. Because the fusion points of the main fibers are connected via the core fibers, this method has the drawback of making the nonwoven fabric stiff and of poor quality.

[0008] Furthermore, in the method disclosed in Patent Document 3 below, the process of thermally shrinking the nonwoven fabric involves increasing the size of molten agglomerates of heat-fusible fibers, which can lead to the drawback of poor surface quality. Furthermore, because molten fibers are generated from ultrafine fiber-generating composite fibers, such as islands-in-sea fibers, the molten agglomerates tend to concentrate at the original composite fiber locations. This also makes the method prone to the drawback of increasing the size of molten agglomerates.

[0009] Furthermore, Patent Document 4 proposes a leather-like article and a manufacturing method thereof, which comprises laminating a polyester ultrafine fiber layer and fusible fibers made of a copolymer polyester having a melting point 10°C or more lower than the polyester ultrafine fiber layer, and subjecting the laminate to a high-speed fluid treatment followed by a molding fusion treatment. The leather-like article manufactured by this manufacturing method comprises a heat-fusible fiber layer and a polyester fiber layer laminated as separate layers and subjected to a heat fusion treatment. Furthermore, the leather-like article uses ultrafine fibers made from a sea-island composite fiber. Therefore, when evaluating abrasion resistance, the ultrafine fibers tend to become tangled and pill when worn due to voids within the fiber bundles generated from the sea part of the sea-island composite fiber. This results in insufficient abrasion resistance and significant deterioration of appearance over time during use. Therefore, the article suffers from the drawback of being unable to achieve both practical abrasion resistance and high-quality appearance maintenance as an artificial leather.

[0010] In addition, Patent Document 5 below discloses an artificial leather that combines good texture, high abrasion resistance, ease of cutting, and shape stability without impregnation with a polymer elastomer such as polyurethane resin. The artificial leather is produced by blending heat-fusible staple fibers in a specific ratio with at least the surface fiber layer of a nonwoven fabric having a multilayer structure of at least two layers, a surface fiber layer and a woven / knitted scrim layer, and then heat-fusing the fabric. While the resulting artificial leather has improved resistance to artificial sebum because it does not contain polyurethane resin, its abrasion resistance is over 20,000 times in a Martindale abrasion test and its feel value is less than 26 cm in a flexibility test. This leaves room for improvement in terms of specific applications, such as car seats, which require both high abrasion resistance and a supple feel. Regarding the production method, after entanglement, the fabric is heat-treated at 200°C using a pin tenter dryer, and simultaneously heat-fusing the heat-fusible staple fibers. While shape stability is good, there is still room for improvement in achieving both abrasion resistance and texture.

[0011] Furthermore, in the following Patent Document 6, in the invention described in Patent Document 5, a portion of the thermoplastic resin formed by melting the heat-fusible staple fibers is exposed on the surface of the surface fiber layer in the form of chunks of a specified size, thereby improving abrasion resistance (more than 40,000 times in an abrasion resistance test using the Martindale method) and feel (bending value of less than 24 cm in a KES pure bending test). However, as in Patent Document 5, after entanglement by spraying a high-speed water stream, heat treatment is performed at 190°C using a pin tenter dryer, and at the same time, heat fusion treatment of the heat-fusible staple fibers is performed, so there is still room for improvement in terms of achieving both abrasion resistance and feel.

[0012] Furthermore, Patent Document 7 states that the present invention provides a novel fiber laminate sheet that has a soft surface texture and moderate firmness, stiffness, and breathability when not impregnated with an elastic polymer, and that the present invention provides a fiber laminate sheet that can be made into artificial leather with a texture more similar to that of natural leather when impregnated with an elastic polymer, as well as artificial leather using the same, and synthetic fiber paper used for the same that makes it easy to separate and entangle single fibers during hydroentanglement, all at low cost; however, the artificial leather described in Patent Document 7 is limited to one that contains a polymer elastomer such as water-based polyurethane. Patent Document 7 also describes the synthetic fiber paper of the present invention as follows: (1) synthetic fiber paper in which fibers are weakly bonded to each other by agglutination; (2) synthetic fiber paper in which the agglutination is released by the pressure of mechanical entanglement, and the fibers are redispersed in the thickness direction to form a three-dimensional entanglement; and (3) synthetic fiber paper in which the binder short fibers soften, shrink, and deform during heat treatment after entanglement, bonding the entangled points, thereby improving the interlayer peel strength compared to when entangled. In order to achieve these series of actions (1) to (3), the synthetic fiber paper contains polyester short fibers as the main component fiber, and is wet-processed synthetic fiber paper containing binder short fibers that are partially bonded to the main component fiber by weak agglutination at the drying temperature during papermaking (100 to 120°C), and then further soften, shrink, and exhibit bond-developing properties when heated at a temperature of 150 to 180°C, which is higher than the drying temperature during papermaking. According to these descriptions, the substance that softens and shrinks is the binder short fiber, and therefore Patent Document 7 does not teach that a portion of the thermoplastic resin formed by melting the heat-fusible short fiber is exposed on the surface of the surface fiber layer in the form of lumps of a predetermined size, as described in Patent Document 6, nor does it state that abrasion resistance or texture is improved. [Prior art documents] [Patent documents]

[0013] [Patent Document 1] Patent No. 5919627 [Patent Document 2] Japanese Patent Application Publication No. 07-216756 [Patent Document 3] Special Publication No. 03-016427 [Patent Document 4] Patent No. 4835181 [Patent Document 5] Patent No. 5685003 [Patent Document 6] Patent No. 6118174 [Patent Document 7] Patent No. 4708494 Summary of the Invention [Problem to be solved by the invention]

[0014] In view of the above-mentioned state of the art, the problem to be solved by the present invention is to provide a recyclable artificial leather that combines a good feel, high abrasion resistance, and a luxurious appearance, and a method for producing the same. [Means for solving the problem]

[0015] As a result of extensive research and experimentation conducted by the present inventors in order to solve the above-mentioned problems, they unexpectedly discovered that the problems could be solved by artificial leather having the following characteristics, and thus completed the present invention. That is, the present invention is as follows.

[0016] [1] An artificial leather comprising at least a surface fiber layer constituting a first surface, and having the following characteristics: (1) The surface fiber layer is composed of at least one type of main fiber and a thermoplastic resin having a melting point that is 20°C or more lower than the melting point of the main fiber; (2) The fineness of the main fiber is 0.01 dtex or more and 0.5 dtex or less; (3) At least a portion of the thermoplastic resin bonds the main fibers together; (4) When the first surface is measured by X-ray CT, the number average volume of the thermoplastic resin in the first surface fiber layer is 5000 μm 3 More than 14000μm 3 is less than or equal to; and (5) The volume number density of the thermoplastic resin in the first surface fiber layer is 1.1 × 10 12 pieces / m 3 Over 3.0 x 10 12 pieces / m 3 Below is; Artificial leather having the above structure. [2] The artificial leather according to [1], wherein the main fiber is a polyester fiber. [3] The artificial leather according to [1] or [2], wherein the thermoplastic resin is a polyester resin. [4] The artificial leather according to any one of the above [1] to [3], wherein the surface fiber layer is entangled with a scrim layer which is a woven fabric. [5] The artificial leather according to any one of [1] to [4], wherein the scrim layer is made of polyester-based resin fibers. [6] The artificial leather according to any one of [1] to [5], wherein when the surface is abraded with a pressure load of 12 kPa in accordance with JIS-L-1096 E method (Martindale method), the scrim is not exposed after less than 50,000 abrasion cycles. [7] The artificial leather according to any one of [1] to [5], wherein the abrasion loss is 21 mg or less when the surface is abraded 50,000 times at a pressure load of 12 kPa in accordance with JIS-L-1096 E method (Martindale method). [8] The following steps: (1) Main fibers and heat-fusible fibers made of a thermoplastic resin having a melting point 20°C to 170°C lower than the melting point of the main fibers are mixed so that the weight ratio of the heat-fusible fibers is 3% to 25%, and then the mixture is entangled on a scrim layer by wet papermaking, and then a surface fiber web entangled with the scrim layer is formed by hydroentanglement treatment or needle punching; and (2) Relaxing the entangled structure of the obtained surface fiber web by thermal annealing shrinkage at a temperature equal to or higher than the melting point of the heat-fusible fibers and lower than the melting point of the main fibers to form a surface fiber layer; The method for producing an artificial leather according to any one of the above [1] to [7], comprising: [9] The manufacturing method according to [8] above, wherein the length of the main fibers in the step (1) is 2.5 mm or more and 90 mm or less.

[10] The manufacturing method according to [8] or [9] above, wherein the fineness of the heat-fusible fiber in the step (1) is 0.5 dtex or more and 2.2 dtex or less. [Effects of the Invention]

[0017] In the artificial leather of the present invention, the thermoplastic resin bonds the main fibers with a fineness of 0.01 dtex to 0.5 dtex together in a relaxed entangled structure. This reduces the number of fibers bonded to one thermoplastic resin (thermal fusion point), resulting in an excellent feel compared to conventional artificial leathers composed solely of polyester. Meanwhile, the density of thermal fusion points per unit volume can be maintained at a certain level, maintaining the entanglement of the fibers and achieving good abrasion resistance. Furthermore, if the artificial leather of the present invention uses polyester fibers as the main fibers and thermoplastic resin and does not contain an elastic polymer such as water-based polyurethane, it will have excellent recyclability and excellent flame resistance due to the ability to suppress gas generation during combustion. [Brief explanation of the drawings]

[0018] [Figure 1] FIG. 2 is a diagram showing an example of the state of clumped resin in a surface fiber layer. [Figure 2] FIG. 10 is a diagram showing another example of the state of lump resin in the surface fiber layer. [Figure 3] FIG. 10 is a diagram showing another example of the state of lump resin in the surface fiber layer. [Figure 4] FIG. 10 is a diagram showing another example of the state of lump resin in the surface fiber layer. [Figure 5] FIG. 10 is a diagram showing another example of the state of lump resin in the surface fiber layer. [Figure 6] FIG. 10 is a diagram showing another example of the state of lump resin in the surface fiber layer. [Figure 7] FIG. 10 is a diagram showing another example of the state of lump resin in the surface fiber layer. [Figure 8] FIG. 10 is a diagram showing another example of the state of lump resin in the surface fiber layer. [Figure 9] FIG. 1 is a conceptual diagram of a thermal annealing shrinkage method. [Figure 10] 1 is a photograph in place of a drawing showing a state in which the thermoplastic resin bonds the main fibers together and the thermoplastic resin is present on the surface of the surface fiber layer in the form of a lump resin. [Figure 11] This is a cross-sectional view of an artificial leather actually produced by the method described in Example 1, which was cut, the cross section was evaluated by X-ray CT, and the image data was subjected to noise removal using a 3D median filter: 2pix. [Figure 12] The cross-sectional view obtained in Figure 11 is binarized under the conditions described above, and the image data is inverted black and white. [Figure 13] This is an enlarged image data of a part (scrim part) of Figure 12. [Figure 14] This is the image data obtained by performing Fill Holes processing on the image data in Figure 13. [Figure 15] This is image data in which the image data from Figure 14 has been color mapped using fiber diameter distribution. 21 indicates the surface layer, 22 the scrim layer, and 23 the back layer. The bright spots seen in the surface and back layers are the heat-sealable resin. [Figure 16] The fiber sheet 11 includes, for example, a scrim 12 which is a woven or knitted fabric, a surface fiber layer (A) 13 which forms the front surface, and a fiber layer (B) 14 which forms the back surface. However, the fiber layer (B) 14 is optional and not an essential element. [Figure 17] The fiber sheet 11 includes a scrim 12 which is a woven or knitted fabric, and a surface fiber layer (A) 13 . DETAILED DESCRIPTION OF THE INVENTION

[0019] Hereinafter, embodiments of the present invention will be described in detail. One embodiment of the present invention is an artificial leather including at least a surface fiber layer constituting a first surface, the artificial leather having the following characteristics: (1) The surface fiber layer is composed of at least one type of main fiber and a thermoplastic resin having a melting point that is 20°C or more lower than the melting point of the main fiber; (2) The fineness of the main fiber is 0.01 dtex or more and 0.5 dtex or less; (3) At least a portion of the thermoplastic resin bonds the main fibers together; (4) When the first surface is measured by X-ray CT, the number average volume of the thermoplastic resin in the first surface fiber layer is 5000 μm 3 More than 14000μm 3 is less than or equal to; and (5) The volume number density of the thermoplastic resin in the first surface fiber layer is 1.1 × 10 12 pieces / m 3 Over 3.0 x 10 12 pieces / m 3 Below is; It is an artificial leather having the above structure.

[0020] The main fibers contained in the surface fiber layer are fibers that account for 60% by mass or more, more preferably 70% by mass or more, and even more preferably 80% by mass or more, based on 100% by mass of the surface fiber layer. There is no particular upper limit, but it may be 99% by mass or less. The main fiber contained in the surface fiber layer is preferably a polyester fiber, a polyamide fiber, an acrylic fiber, or a polyolefin fiber from the viewpoints of strength, ease of manufacturing ultrafine fibers, general market availability, etc. However, as described above, in consideration of applications requiring durability such as car seats, polyethylene terephthalate is preferred because the fiber itself does not yellow even when exposed to direct sunlight for a long period of time and has excellent color fastness. Furthermore, from the viewpoint of reducing the environmental load, chemically recycled or material recycled polyethylene terephthalate, or polyethylene terephthalate made from plant-derived raw materials, etc. are even more preferred.

[0021] Suitable polyester fibers as the main fibers constituting the surface fiber layer include polyethylene terephthalate (PET), polytrimethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polylactate, copolymers thereof, etc. Suitable polyamide fibers include nylon, meta-aramid, para-aramid, copolymers thereof, etc. Suitable acrylic fibers include acrylic acid ester or methacrylic acid ester polymers, copolymers thereof, etc. Suitable polyolefin fibers include polyethylene, polypropylene, polybutene, polystyrene, copolymers thereof, etc. These fibers can be used alone, or fibers of various polymers can be mixed in any ratio.

[0022] If not only the main fiber but also a thermoplastic resin having a melting point 20°C or more lower than that of the main fiber contained in the surface fiber layer described below, and the scrim are made of a polyester-based resin, then, for example, used PET can be recovered from clothing or beverage bottles, processed into recycled PET resin, and used artificial leather can be manufactured using this recycled PET resin. Further, used (end-of-life) artificial leather can be recycled and processed into, for example, insulation material or filter material, and PET can be recovered from used insulation material or filter material, thereby producing recyclable artificial leather suitable for a circular economy.

[0023] The main fiber has a fineness of 0.5 dtex or less, preferably 0.35 dtex or less, and more preferably 0.2 dtex or less, from the viewpoint of easily obtaining a texture similar to that of natural leather and a suede-like or nubuck-like surface feel, while the fineness is 0.01 dtex or more, more preferably 0.03 dtex or more, from the viewpoints of production efficiency, production stability, and abrasion resistance during fiber production. The main fiber may be a fiber directly spun by a melt spinning method, a fiber obtained by a wet spinning method, or an ultrafine fiber obtained by removing the sea component from a sea-island fiber in which a copolyester is used as the sea component and a regular polyester is used as the island component.

[0024] The main fiber may contain or have attached thereto additives, such as titanium oxide, various antioxidants, light fasteners, antistatic agents, flame retardants, softeners, fastness improvers, pigments such as carbon black, and dyes, as long as the desired effect is achieved.

[0025] The thermoplastic resin constituting the surface fiber layer and having a melting point 20°C to 170°C lower than that of the main fiber is preferably a polyester resin, a polyamide resin, an acrylic resin, a polyolefin resin, or the like, from the viewpoint of availability. Suitable polyester resins include polyethylene terephthalate, polytrimethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polylactate, and copolymers thereof. Suitable polyamide resins include nylon and copolymers thereof. Suitable acrylic resins include polymers of acrylic acid esters or methacrylic acid esters, and copolymers thereof. Suitable polyolefin resins include polyethylene, polypropylene, polybutene, polystyrene, and copolymers thereof.

[0026] The thermoplastic resin does not necessarily have to be made of only a single polymer, and may be a mixture of multiple types of polymers. The thermoplastic resin may contain or have attached thereto additives, such as titanium oxide, various antioxidants, light stabilizers, antistatic agents, flame retardants, softeners, fastness improvers, pigments such as carbon black, and dyes, as long as the desired effect is achieved. The thermoplastic resin has a melting point that is 20°C to 170°C lower than that of the main fiber. When two or more types of main fiber are used, the melting point must be 20°C to 170°C lower than that of the main fiber with the lowest melting point. When the thermoplastic resin is a mixture of multiple polymers, the thermoplastic resin with the highest melting point must have a melting point that is 20°C to 170°C lower than that of the main fiber with the lowest melting point. Regarding the melting point range, the abrasion resistance and appearance quality described in the present application can be achieved within the above range. However, from the viewpoint of maintaining particularly good appearance quality, the melting point of the thermoplastic resin should be preferably 40°C to 150°C lower, more preferably 40°C to 100°C lower, than that of the main fiber.

[0027] The thermoplastic resin must be in the form of chunks and exposed on the surface of the surface fiber layer. If it is not exposed on the surface, the main fibers present on the surface are not sufficiently held together by the resin fusion, and the fibers are prone to falling off and breakage, resulting in an artificial leather that does not have sufficient abrasion resistance. In addition, part or all of the thermoplastic resin bonds the main fibers together. If the thermoplastic resin does not bond the main fibers together, the main fibers are not sufficiently held together, and the fibers are prone to falling off and breakage, resulting in an artificial leather that does not have sufficient abrasion resistance or strength.

[0028] Furthermore, the thermoplastic resin must be present in the form of chunks in the cross section of the surface fiber layer. If it is present only on the surface and not in the form of chunks in the cross section, the main fibers will not be sufficiently held together by the resin fusion, and the artificial leather will not have satisfactory abrasion resistance, and the density of the surface fiber layer will not be sufficiently increased, making it impossible to achieve the luxurious, moist texture that is characteristic of artificial leather.

[0029] In this embodiment, the thermoplastic resin bonds the main fibers together and has a number average volume of 5000 μm 3 More than 14000μm 3 The number average volume of the thermoplastic resin must be 14,000 μm or less. 3If the number average volume is more than 5000 μm, the proportion of the same thermoplastic resin bonding multiple main fibers will be high, which will tend to cause the material to feel rough to the touch and will not be able to exhibit a satisfactory sense of luxury as artificial leather. 3 If the number average volume is less than 5500 μm, the particle size will not be large enough to surround one main fiber, the main fiber will not be held effectively, and the abrasion resistance required for car interiors will not be achieved. 3 More than 13000μm 3 Less than or equal to 5500 μm, preferably 3 More than 12000μm 3 The following is the result.

[0030] In the first surface fiber layer, the volumetric number density, which is the number of thermoplastic resin particles per unit volume, is 1.1 × 10 12 pieces / m 3 Over 3.0 x 10 12 pieces / m 3 The number of particles per unit volume of the thermoplastic resin must be 1.1 x 10 12 pieces / m 3 If the volume number density of the thermoplastic resin is less than 3.0×10, it is not possible to bond a plurality of main fibers with a plurality of thermoplastic resins, and many fiber bundles fall off when worn, making it impossible to exhibit sufficient abrasion resistance. 12 pieces / m 3 If the volume number density of the thermoplastic resin is more than 1.1×10, the first surface fiber layer becomes too hard and the supple, luxurious feel required for artificial leather cannot be obtained. 12 pieces / m 3 Over 2.0 x 10 12 pieces / m 3 Less than or equal to 1.1 × 10 12 pieces / m 3 Over 1.6 x 10 12 pieces / m 3 is

[0031] Another embodiment of the present invention is a method for producing a method for manufacturing a semiconductor device comprising the steps of: (1) Main fibers and heat-fusible fibers made of a thermoplastic resin having a melting point 20°C to 170°C lower than the melting point of the main fibers are mixed so that the weight ratio of the heat-fusible fibers is 3% to 25%, and then the mixture is entangled on a scrim layer by wet papermaking, and then a surface fiber web entangled with the scrim layer is formed by hydroentangling or needle punching; and (2) Relaxing the entangled structure of the obtained surface fiber web at a temperature equal to or higher than the melting point of the heat-fusible fibers and lower than the melting point of the main fibers, preferably by thermal annealing shrinkage, to form a surface fiber layer; The method for producing the artificial leather comprises the steps of:

[0032] The scrim layer constituting the artificial leather of this embodiment is preferably a woven or knitted fabric, as it functions as a core material and can stabilize the production of the papermaking sheet in the papermaking process and increase the mechanical strength of the resulting artificial leather. The material of the scrim layer is preferably the same polymer as the main fiber in terms of color uniformity in dyeing, and in the case of knitted fabrics, a single knit knitted at a gauge of 22 to 28 is preferred. Woven fabrics are even more preferred because they can achieve higher dimensional stability and strength than knitted fabrics. The yarn constituting the woven fabric may be monofilament or multifilament. The single fiber fineness of the yarn is preferably 5.5 dtex or less, as this facilitates the production of a flexible artificial leather using an entangled sheet. The form of the yarn constituting the woven fabric is preferably raw multifilament yarn such as polyester or polyamide, or textured yarn that has been subjected to false twist processing and twisted at a twist rate of 0 to 3000 T / m. The multifilament may be a conventional one, and for example, 33 dtex / 6 f, 55 dtex / 24 f, 83 dtex / 36 f, 83 dtex / 72 f, 110 dtex / 36 f, 110 dtex / 48 f, 167 dtex / 36 f, 166 dtex / 48 f, etc. of polyester, polyamide, etc. are preferably used. The yarns constituting the woven fabric may be multifilament long fibers. In order to obtain artificial leather that is soft and has excellent mechanical strength, the weave density of the yarns in the woven fabric is preferably 30 yarns / inch or more and 150 yarns / inch or less, more preferably 40 yarns / inch or more and 100 yarns / inch or less. In order to provide good mechanical strength and an appropriate feel, the weight of the woven fabric should be 20 g / m 2 More than 150g / m 2 The following are preferred: The presence or absence of false twist processing in the woven fabric, the number of twists, the single fiber fineness of the multifilament, the weave density, etc. contribute to the entanglement with the constituent fibers of the main fiber layer, the flexibility of the artificial leather, as well as the mechanical properties such as seam strength, tear strength, tensile strength / elongation, and stretchability, and therefore may be selected appropriately depending on the target physical properties and application.

[0033] The length of the main fiber in step (1) is not particularly limited, but is preferably 2.5 mm or more and 90 mm or less. If the length of the main fiber is within this range, hydroentanglement with the scrim layer is sufficient. If the length of the main fiber is 2.5 mm or less, the entanglement effect with the scrim layer is not sufficiently achieved in the entanglement step, and relative peeling between the main fiber layer and the scrim layer is likely to occur, which may cause quality defects such as poor adhesion and poor appearance. The length of the main fiber is more preferably 2.5 mm or more and 20 mm or less, and even more preferably 3 mm or more and 10 mm or less.

[0034] The artificial leather of this embodiment can include at least a surface fiber layer that constitutes a first surface. For example, in the case of an artificial leather consisting of a surface fiber layer and a scrim layer, the first surface (upper surface) becomes the surface (front side), and the back surface of the scrim layer becomes the second surface (lower surface). Also, in the case of an artificial leather of this embodiment consisting of three layers: surface fiber layer / scrim layer / back fiber layer, the back surface of the back fiber layer becomes the second surface. In addition, when a surface fiber layer / scrim layer / back fiber layer configuration is adopted as one aspect of this embodiment, the material constituting the back fiber layer is not particularly limited, but from the viewpoint of achieving good recyclability, it is preferably the same as the main fiber and / or thermoplastic resin of the surface fiber layer. Furthermore, when a back fiber layer is included, it may be made of a material different from that of the surface fiber layer, for example, by adding a flame retardant, to impart desired properties.

[0035] In Fig. 16, the fiber sheet 11 includes, for example, a scrim 12 which is a woven or knitted fabric, a surface fiber layer (A) 13 which forms the front surface, and a fiber layer (B) 14 which forms the back surface. However, the fiber layer (B) 14 is optional and not an essential element. In Fig. 17, the fiber sheet 11 includes the scrim 12 which is a woven or knitted fabric and the surface fiber layer (A) 13.

[0036] A preferred method for producing the artificial leather of this embodiment involves heat-treating a nonwoven fabric structure having a surface fiber layer formed by mixing at least one type of main fiber with fully fusible heat-fusible fibers having a melting point that is 20°C to 170°C lower than the melting point of the main fiber, thereby melting the heat-fusible fibers and forming a mass of thermoplastic resin in the surface fiber layer. The heat-fusible fibers are preferably full-fusible fibers so that the fused bulk resin has a sufficient number of points at which the fused main fibers are bonded together after melting. Compared with sheath-core fibers using a low-melting-point thermoplastic resin in the sheath or side-by-side fibers using a low-melting-point thermoplastic resin on only one side, full-fusible fibers have more points at which the main fibers are bonded together and a large amount of fusible components in the fused parts, so that the fusion strength is sufficient. Furthermore, since the fusion points are not continuously located in the vicinity of each other via the heat-fusible fibers, the full-fusible fibers are also preferred because they tend to have a softer feel.

[0037] The heat-fusible fibers (heat-fusible yarns) constituting the surface fiber layer and having a melting point 20°C to 170°C lower than that of the main fiber are preferably polyester fibers, polyamide fibers, acrylic fibers, or polyolefin fibers from the viewpoint of availability. Suitable polyester fibers include polyethylene terephthalate, polytrimethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polylactate, and copolymers thereof. Suitable polyamide fibers include nylon and copolymers thereof. Suitable acrylic fibers include polymers of acrylic acid esters or methacrylic acid esters, and copolymers thereof. Suitable polyolefin fibers include polyethylene, polypropylene, polybutene, polystyrene, and copolymers thereof.

[0038] The melting point in this specification refers to a value measured by a DSC (differential scanning calorimeter). The differential scanning calorimeter measures the difference in heat between a measurement sample and a reference material, and calculates the melting point of the measurement sample. Specifically, the melting point was determined as the peak top of the endothermic peak observed when the temperature was raised from 25°C to 250°C at a rate of 10°C / min.

[0039] The heat-fusible fiber does not necessarily have to be composed of a single polymer; it may be a mixture of multiple polymers. From the viewpoints of high fusion strength and uniformity in dyeing, it is preferable to use the same polymer system as the main fiber. The heat-fusible fiber can be a fiber directly spun by a melt spinning method, a fiber obtained by a wet spinning method, or an ultrafine fiber obtained by removing the sea component from a sea-island fiber using a copolymer polyester as the sea component and a regular polyester as the island component. The fineness of the heat-fusible fiber is preferably 0.5 dtex to 2.2 dtex in consideration of the size of the molten block of thermoplastic resin. A fineness of 2.2 dtex or less allows the molten block of thermoplastic resin to be uniformly dispersed on the surface of the surface fiber layer, resulting in excellent appearance and texture. The fineness of the heat-fusible fiber is more preferably 0.6 dtex to 2.0 dtex, even more preferably 0.7 dtex to 1.5 dtex.

[0040] The heat-fusible fibers may contain or have attached thereto additives, such as titanium oxide, various antioxidants, light-resistant agents, antistatic agents, flame retardants, softeners, fastness improvers, pigments such as carbon black, and dyes, as long as the desired effects are achieved.

[0041] Methods for forming the surface fiber layer include using the main fibers and / or heat-fusible fibers in the form of short fibers and entangling the fibers to form a nonwoven structure using a papermaking method, a carding method, an air-laying method, or the like. From the viewpoint of uniform dispersion of the constituent fibers and ease of use of ultrafine fibers, it is particularly preferred that the surface fiber layer be formed by a papermaking method.

[0042] In addition, in this embodiment, the layers can be entangled using a hydroentanglement method known as a spunlace method, a needle punch method, or the like, but the hydroentanglement method is preferred as it does not destroy the structure of the woven or knitted fabric that is the scrim layer.

[0043] "Heat fusion in a relaxed state of intertwined structure (thermal annealing shrinkage)" The heat-sealing treatment in this embodiment can be performed using a drum dryer, a contact dryer such as a calendar roll, a biaxially stretching film stretcher, or an air-through dryer such as a pin tenter dryer. The treatment temperature is at least 5°C higher, preferably at least 10°C higher, than the melting point of the heat-sealing fibers, which are made of a thermoplastic resin and have a melting point 20°C to 170°C lower than that of the main fiber, constituting the surface fiber layer, and is 240°C or lower, preferably 200°C or lower. If the difference between the treatment temperature and the melting point of the thermoplastic fiber is less than 5°C, sufficient heat-sealing effect may not be achieved. If the treatment temperature exceeds 240°C, the polyester main fiber may melt, impairing the luxurious surface quality and / or insufficient abrasion resistance may be achieved.

[0044] FIG. 9 is a conceptual diagram of thermal annealing shrinkage. To achieve the desired physical properties in the artificial leather of this embodiment, it is necessary to bond the main fibers together with a molten thermoplastic resin while the entangled structure of the main fibers is relaxed during heat fusion (thermal bonding). The mechanism by which the artificial leather of this embodiment achieves both abrasion resistance and texture can be explained by the complex correlation between the artificial leather's unique, luxurious texture and the size and density of the thermoplastic resin present in the surface fiber layer. In other words, it is necessary to design the distribution density of the thermoplastic resin in the main fiber layer while keeping the size of the thermoplastic resin below a certain value. If the size of the thermoplastic resin becomes too large, the finger will feel uneven when touched, compromising the smooth texture, making it impossible to achieve the luxurious feel desired for artificial leather. On the other hand, if the distribution density of the thermoplastic resin becomes small, the bonding effect between the main fibers is not sufficient, and the frequency with which fiber bundles fall off en masse from the substrate during wear increases, resulting in a large amount of abrasion weight loss, an inability to maintain a sufficient product life, and a tendency for changes in appearance, such as exposure of the scrim, to occur, and the required performance of the product cannot be fully met.

[0045] The size and density of the thermoplastic resin (heat-fused points) are important for achieving the effects of the present invention, and the thermoplastic resin can be evaluated by cutting the artificial leather vertically and observing it with an optical microscope or electron microscope, or by measuring 3D images using CT or MRI, etc. Accurate evaluation of the position, density, shape, and size of the heat-fused resin not only on the surface but also inside the material is required, and accurate analysis and evaluation can be achieved by sequential image analysis of the cross section using X-ray CT, appropriate image processing procedures, and mathematical analysis.

[0046] In order to achieve the effects of the present invention, it is necessary to control the density of heat-sealing points during heat-sealing, and it is preferable to relax the nonwoven fabric structure when the thermal annealing effect is exerted. Preferably, the surface fiber web entangled with the scrim layer is slackened and shrunk in the MD direction, which is the direction in which the nonwoven fabric structure advances during the manufacturing process, and in the CD direction, which is the direction perpendicular to the MD direction, during the heat-sealing process. This results in a relaxed entangled structure, as shown in Figure 9, i.e., the main fibers are fixed in a relaxed state. This makes it possible to achieve the desired size and density of the thermoplastic resin (heat-sealing points), compared to the conventional method in which heat-sealing is performed while tensioning and shrinking using a pin tenter, and thus allows the production of artificial leather with high abrasion resistance and texture. In Table 1 below, "+" in "thermal annealing shrinkage" means that the heat fusion treatment was performed in a shrunk state of the nonwoven fabric, "0" means that the heat fusion treatment was performed without stretching or shrinking the nonwoven fabric, and "-" means that the heat fusion treatment was performed in a stretched state of the nonwoven fabric.

[0047] The nonwoven fabric for artificial leather obtained by the above method can be used as a suede- or nubuck-like artificial leather by raising the surface of the surface fiber layer and dyeing it. The raising can be performed by a known method such as buffing with sandpaper. In this case, if the raising is performed before the heat-fusible fibers of the surface fiber layer are heat-fused, a suede-like surface texture can be obtained. On the other hand, if the raising is performed after the heat-fusible fibers are heat-fused, a nubuck-like surface texture can be obtained.

[0048] The dyeing treatment is not particularly limited. For example, when the main fiber is a polyester fiber, a disperse dye is generally used. The dyeing method can be a conventional method well known to dyeing processors, and for artificial leather, a jet dyeing machine is preferably used in order to achieve even dyeing. The artificial leather dyed in this manner is reduced and washed by soaping or in the presence of a chemical reducing agent to remove excess dye. The conditions for reduction and washing are not particularly limited, and may be selected according to the chemical stability of the main fiber and thermoplastic resin. Basic and acidic reducing agents can be used according to conventional methods without any particular restrictions.

[0049] The thickness of the artificial leather of this embodiment is preferably 0.40 mm to 1.50 mm. By making the thickness of the artificial leather within the range of 0.40 mm to 1.50 mm, the thickness of the ultrafine fiber layer can be sufficiently ensured while maintaining sufficient fusion points per unit area and entanglement between the fibers in the surface ultrafine fiber layer, thereby achieving both a soft feel and sufficient stretchability.

[0050] The weight of the artificial leather of this embodiment is 100 g / m 2 ~400g / m 2 It is preferable that the basis weight is 100 g / m 2 ~400g / m 2 By doing so, it is possible to achieve both a soft feel and a moderate hardness. The basis weight is more preferably 200 g / m 2 ~300g / m 2 is.

[0051] The artificial leather of this embodiment has a feel value (flexural rigidity per unit width in KES pure bending measurement) of 1.0 gfcm, which is a substitute characteristic for feel and is measured by the method described below, to provide a favorable feel for use as artificial leather. 2The feel value is preferably less than 1.0 gfcm / cm. Although there is no particular limitation on the measurement of the feel value, a suitable method is to use a 20 cm wide sample, evaluate it using a commercially available KES pure bending tester, and convert the obtained bending stiffness per unit width. 2 By setting the value to less than 1 / cm, the good quality characteristic of artificial leather can be obtained.

[0052] In order to have good abrasion resistance when used as an artificial leather, the artificial leather of this embodiment preferably has a scrim that does not become exposed when the surface is abraded under a pressure load of 12 kPa in accordance with JIS-L-1096 E method (Martindale method) less than 50,000 times.

[0053] The artificial leather of this embodiment preferably exhibits flame retardancy of grade 4 or higher in a flammability test conforming to the U.S. Federal Motor Vehicle Safety Standard "FMVSS No. 302." By maintaining flame retardancy of grade 4 or higher, the artificial leather can meet the flame resistance standards for automobiles, aircraft, and the like, thereby broadening the range of applications to which it can be applied when used as artificial leather. [Example]

[0054] The present invention will be specifically described below based on examples and comparative examples, but the present invention is not limited to these examples. The physical properties used in the examples were measured by the following methods.

[0055] (1) Evaluation of number average volume and volume number density of thermoplastic resin (lump resin) The volume of the thermoplastic resin mass was observed using an X-ray CT device (Rigaku Corporation's "High-Resolution 3D X-ray Microscope Nano3DX"), with the entire thickness of the artificial leather observed. 3D images were taken with the center of the thickness cross section as the center point of the observation area. Image measurement was performed using a copper X-ray target under conditions of an X-ray tube voltage of 40 kV, a tube current of 30 mA, an exposure time of 12 seconds per image, and a spatial resolution of 1.08 μm / pixel. Using the same procedure, 1,000 images were taken per 180° of rotation, and 3D measurement data was obtained. The detailed process for processing and analyzing the 3D measurement data obtained above is described below. The image analysis software used was ImageJ (version 1.51j8, National Institutes of Health, USA). (i: Image rotation) The three-dimensional image is rotated so that the surface direction of the artificial leather coincides with the surface direction consisting of the xz axes, and the thickness direction of the artificial leather coincides with the y axis. (ii) Trimming: Trim the 3D image into a rectangular parallelepiped. In this case, the y-axis should be set to a range that includes the entire thickness and does not include excessive space outside the membrane. For the x-axis and z-axis, after determining the y-axis range, the maximum range is taken so that no pixels outside the measurement field of view are included within the trimmed rectangular parallelepiped. (iii: Setting the axes) The number of pixels in the x-axis direction of the cropped image is set to x0, the number of pixels in the y-axis direction to y0, and the number of pixels in the z-axis direction to z0. (iv: Filtering) A median filter is applied with a radius of 2 pix. (v: Region division) The Otsu method is applied to divide the regions. At this time, in order to clearly distinguish between light and dark, the pixel brightness values ​​are set so that the air portion that does not contain artificial leather is 0 and the main fiber portion that makes up the artificial leather is 255. (vi: Segmentation) The image processing method segmentation is applied to pixels with a brightness value of 255. Structures with a pixel count (pix) of 10,000 or less that are connected three-dimensionally into a single region with a brightness value of 255 are considered noise, and their brightness value is changed to 0 to remove them. (vii: Noise Removal) Of the pixels with a brightness value of 0, pixels with a brightness value of 0 that are three-dimensionally surrounded by pixels with a brightness value of 255 are considered to be noise, and their brightness values ​​are changed to 255 to remove them. (viii: Calculation of porosity) A two-dimensional original image of the xz plane is cut out from the three-dimensional image at a thickness of 1 pixel in the thickness direction, and the porosity on that plane is calculated using the following formula: Porosity = Number of pixels with brightness value 0 / Total number of pixels and calculate it. (ix: Thickness distribution of porosity) The above (viii) is carried out for all y data to determine the distribution of porosity in the y-axis direction. (x: Calculation of the size of high-intensity pixels) The size of pixels with an intensity value of 255 is calculated using the Thickness method. This results in a 3D image in which the intensity value for each pixel is the diameter of the largest sphere that would fit within that location. The Thickness method is described in the paper "A new method for the model-independent assessment of thickness in three-dimensional images," T. Hildebrand and P. Rueesgsegger, J. of Microscopy, 185 (1996) 67-75, and can be implemented, for example, using the BoneJ Thickness plugin for the image analysis software ImageJ. Furthermore, in the image obtained here, structures smaller than 12 μm are considered to be main fibers and are removed from the analysis, so the image intensity value of pixels smaller than the number of pixels corresponding to 12 μm is changed to 0. (xi: Binarization) The image obtained in (x) above is binarized by setting all pixels with a brightness value other than 0 to 255 and leaving pixels with a brightness value of 0 as 0. (xii: Particle analysis) Three-dimensional particle analysis is performed on the image obtained in (xi) above. A continuous three-dimensional area with a brightness value of 255 is considered to be one particle, and the center coordinates (XC, YC, ZC) of each particle and the number of pixels in the continuous structure are calculated. (xiii: Definition of surface, scrim layer, and back surface) In the data of the porosity distribution obtained in (ix) above, the 95% range is used for analysis (excluding the outermost surfaces of the surface and the back surface). Therefore, on the surface of the artificial leather, the value of the y-axis farthest from the front side where the porosity is 0.95 or more is defined as y1. When including the scrim layer, the numerical value of the porosity in (viii) and the portion where fibers with a fineness of 100 dtex or more appear are defined as the front-end part, and its coordinate is y2. (xiv: Calculation of total number of pixels and data analysis) For all the particles obtained in (xii) above, for the particles whose coordinate values satisfy y1 < YC < y2, the number of particles and the total sum of the pixel numbers of the particles are determined. Number-average volume (μm 3 ) = Total sum of pixel numbers of particles * p * p * p ÷ Number of particles Volume number density (10 12 per m 3 ) = Number of particles ÷ (|y2 - y1| * p * x0 * p * z0 * p) Here, p is the pixel size (m / pix), which is the actual size (m) of 1 pixel (pix).

[0056] (2) Fusing state of thermoplastic resin (block resin) Using the figures, the state of the block resin and its determination will be described. Figure 1 is an example where it is exposed on the surface of the surface fiber layer but the main fibers are not adhered to each other. Figure 2 is an example where it is exposed on the surface and the main fibers are adhered to each other. Figure 3 is an example where it is not exposed on the surface but the main fibers are adhered to each other. Figure 4 is an example where it is exposed on the surface and the main fibers are adhered to each other. Figure 5 is an example where it is exposed on the surface but the main fibers are not adhered to each other. Figure 6 is an example where the heat-fused fibers are not melted and is not referred to as a block resin. Figure 7 is an example where sheath-core fibers are used as the heat-fused fibers, and the heat-fused fibers remain in the fiber shape and are not referred to as a block resin. Figure 8 is an example where it is exposed on the surface but the main fibers are not adhered to each other. In the figures, 1 is the main fiber, 2 is the block resin, 3 is the unmelted resin, and 4 is the sheath-core fiber. Here, "the main fibers are adhered to each other" means a state where at least two or more main fibers penetrate through the inside of the block resin (thermoplastic resin) and are physically bonded.

[0057] (3) Fineness Ten randomly selected points on the front or back fiber layer sample of the artificial leather were photographed using a microscope at a magnification of 2500x, and the diameters of the fibers at 50 points were measured. The average value of these measurements was calculated as the average fiber diameter. The fineness [dtex] of the main fiber was calculated from the average fiber diameter and the density of the main fiber. In addition, artificial leather was immersed in ethanol, wrapped in gelatin capsules, and freeze-dried in liquid nitrogen. The capsules were then cut with a knife, and the cut cross section of the sample, which had been returned to room temperature, was observed using a scanning electron microscope (JSM-5610, manufactured by JEOL Ltd.) at a working distance of 10 mm and a magnification of 200x. The thickness of the woven yarns making up the scrim layer was measured at five points on each of the 20 images obtained, and the fineness of the woven yarns making up the scrim layer was determined. The fineness of the heat-fusible yarn is the fineness of the raw short fibers, and was evaluated using a scanning electron microscope. Specifically, adhesive carbon tape was attached to the evaluation stage, 0.05 g of the raw short fibers was placed on top of it, and excess heat-fusible yarn was removed with an air duster to obtain a sample. The sample was observed under conditions of WD = 10 mm and magnification 200x, and the thickness was determined by measuring five points on each of 20 images obtained.

[0058] (4) Abrasion resistance and wear loss The sample surface was abraded under a pressure load of 12 kPa using the method specified in JIS-L-1096 Method E (Martindale method). The evaluation criteria for this test method were the number of abrasions required until the sample surface layer was abraded and exposed to the scrim, and the evaluation was divided into the following evaluation criteria (grades). (Evaluation criteria) XX: After 5,000 abrasion cycles, significant fiber loss occurred, making it impossible to evaluate. ×: The scrim is exposed after less than 30,000 abrasion cycles. △: The scrim is exposed after 30,000 or more and less than 40,000 abrasion cycles. ○: The scrim is exposed after 40,000 or more and less than 50,000 abrasion cycles. ◎: The scrim is exposed after 50,000 or more abrasions. In addition, artificial leather samples (circular, 40 mm in diameter) specified in JIS-L-1096 E method (Martindale method) were subjected to a pressure load of 12 kPa and abraded 50,000 times, and the weight change [mg] was evaluated as the abrasion loss. The measurement was carried out three times, and the average was used as the result.

[0059] (5) Melting point To measure the melting point of the heat-fused fiber, the heat-fused fiber was placed in a nitrogen atmosphere and heated to 250°C at a rate of 10°C / min using aluminum as the reference material on a TA Instruments DSCQ100. The fiber was then rapidly cooled and heated a second time under the same conditions. The melting point was determined by the top of the endothermic peak that appeared.

[0060] (6) Texture evaluation The resulting dyed artificial leather samples were cut into 25cm squares and arranged on a table with the surface facing up. 20 blindfolded test subjects (10 men and 10 women, two from each age group ranging from their 20s to 60s) were asked to test the texture of the raised surface. At the same time, a similar test was also conducted on natural suede, and a sensory evaluation was conducted on the suppleness and luxurious feel of the surface on a 5-point scale (suede being 5 points), with scores rounded to two decimal points. 〇: Average sensory evaluation score is 3.5 points or more △: Average score of sensory evaluation is 2.5 points or more and less than 3.5 points ×: Average score of sensory evaluation is 2.5 points or less

[0061] [Example 1] Polyethylene terephthalate fibers with a single fiber fineness of 0.15 dtex and a melting point of 255°C were produced by the direct spinning method and cut to a length of 5 mm to form the main fiber. Fully meltable heat-fusible fibers (Casven 8000 manufactured by Unitika Ltd.) with a single fiber fineness of 0.7 dtex and a length of 5 mm and made of polyethylene terephthalate copolymer with a melting point of 178°C were used as the heat-fusible fibers. These short fibers were dispersed in water at a weight ratio of main fiber:heat-fusible yarn of 90:10 to prepare a slurry. A papermaking method was used to produce a 130 g / m2 sheet from this slurry. 2A papermaking sheet for surface fiber was produced. Also, polyethylene terephthalate fibers with a single fiber fineness of 0.15 dtex and a melting point of 255°C were produced by the direct spinning method and cut to a length of 5 mm to form the main fiber. Fully meltable heat-fusible fibers (Casven 8000 manufactured by Unitika Ltd.) with a single fiber fineness of 0.7 dtex and a length of 5 mm and made of polyethylene terephthalate copolymer with a melting point of 178°C were used as the heat-fusible fibers. These short fibers were dispersed in water at a weight ratio of main fiber:heat-fusible fiber = 97:3 to prepare a slurry. A papermaking method was used from this slurry to produce a paper with a basis weight of 50 g / m. 2 These two layers were made of polyethylene terephthalate fiber with a basis weight of 100 g / m², with a combined MD and CD density of 120 (threads / 2.54 cm) and a density of 166 dtex / 48 f. 2 The resulting three-layer laminate was entangled by spraying a high-speed water jet from a straight-flow jet nozzle onto the resulting three-layer laminate, and then dried at 130°C for 5 minutes using an air-through dryer to obtain a three-layer nonwoven fabric.

[0062] The surface of the surface fiber layer of the resulting nonwoven fabric was buffed with 400-mesh sandpaper to give a raised texture. The nonwoven fabric was then placed in a Toyo Seiki Seisakusho X4HDHT biaxial stretching tester, with the fabric slackened to a shrinkage of 5% in both the MD and CD directions, and the centers of both sides and the four corners were clamped with compressed air grips. The nonwoven fabric was then thermally annealed in a chamber at 190°C for 5 minutes to yield a nonwoven fabric for artificial leather. It was then dyed at 130°C using a blue disperse dye (BlueFBL, manufactured by Sumitomo Chemical) in a jet dyeing machine and reduced at 80°C to produce a suede-like artificial leather. The manufacturing conditions and evaluation results for the resulting artificial leather are shown in Table 1.

[0063] [Example 2] Suede-like artificial leather 2 was obtained in the same manner as in Example 1, except that the weight ratio of main fiber:thermofusible fiber in the back surface fiber layer was set to 95:5. The production conditions and evaluation results of the obtained artificial leather are shown in Table 1 below.

[0064] [Example 3] The surface fiber sheet weight is 110g / m 2 Except for changing the single fiber fineness of the heat-fusible fibers to 1.1 dtex, a suede-like artificial leather 3 was obtained in the same manner as in Example 1. The production conditions and evaluation results of the obtained artificial leather are shown in Table 1 below.

[0065] [Example 4] The single fiber fineness of the heat-fusible fiber is 1.1 dtex, the weight ratio of the surface fiber sheet is main fiber: heat-fusible fiber = 92:8, and the basis weight of the surface fiber sheet is 130 g / m 2 Except for the above, suede-like artificial leather 4 was obtained in the same manner as in Example 1. The production conditions and evaluation results of the obtained artificial leather are shown in Table 1 below.

[0066] [Example 5] The weight ratio of the surface fiber sheet is 93:7, the main fiber: heat-melting fiber, and the surface fiber sheet weight is 80g / m. 2 Except for the above, suede-like artificial leather 5 was obtained in the same manner as in Example 1. The production conditions and evaluation results of the obtained artificial leather are shown in Table 1 below.

[0067] [Example 6] Suede-like artificial leather 6 was obtained in the same manner as in Example 1, except that the fineness of the heat-fusible fibers was 1.1 dtex, the weight ratio of the surface fiber sheet was main fiber:heat-fusible yarn = 88:12, and the weight ratio of the back fiber sheet was main fiber:heat-fusible fiber = 95:5. The production conditions and evaluation results of the obtained artificial leather are shown in Table 1 below.

[0068] [Example 7] The surface fiber sheet weight is 110g / m 2 , the basis weight of the backside fiber sheet is 50g / m 2 Suede-like artificial leather 7 was obtained in the same manner as in Example 1, except that the weight ratio of the surface fiber sheet was main fiber:thermofusible yarn = 87:13 and the weight ratio of the back fiber sheet was main fiber:thermofusible yarn = 95:5. The production conditions and evaluation results of the obtained artificial leather are shown in Table 1 below.

[0069] [Example 8] The fineness of the heat-sealing fiber is 0.5 dtex, and the weight of the surface fiber sheet is 110 g / m 2 The weight ratio of the backside fiber sheet was set to 95:5 (main fiber: heat-melting fiber), and the base fabric was heated at 190°C for 5 minutes using a pin tenter dryer without sagging in the MD and CD directions, and suede-like artificial leather 8 was obtained in the same manner as in Example 1, except that thermal annealing shrinkage was not performed.

[0070] [Comparative Example 1] A suede-like artificial leather 9 was obtained in the same manner as in Example 1, except that the base fabric was heated at 190°C for 5 minutes using a pin tenter dryer without sagging in the MD and CD directions and no thermal annealing shrinkage was performed. The production conditions and evaluation results of the obtained artificial leather are shown in Table 1 below.

[0071] Comparative Example 2 The surface fiber sheet weight is 140g / m 2 The weight ratio of the surface fiber sheet was 95:5 (main fiber:thermofusible fiber), and the weight ratio of the back fiber sheet was 95:5 (main fiber:thermofusible fiber). The fabric was heated at 190°C for 5 minutes in a pin tenter dryer without slackening in the MD or CD directions, and no thermal annealing shrinkage was performed, to obtain suede-like artificial leather 10 in the same manner as in Example 1. The production conditions and evaluation results of the obtained artificial leather are shown in Table 1 below.

[0072] Comparative Example 3 The length of the main fiber is 2 mm, the single fiber fineness of the heat-sealing fiber is 1.1 dtex, and the basis weight of the surface fiber sheet is 110 g / m 2 The fabric was heated at 190°C for 5 minutes using a pin tenter dryer without slackening in the MD and CD directions, and no thermal annealing shrinkage was performed, to obtain suede-like artificial leather 11 in the same manner as in Example 1. The production conditions and evaluation results of the obtained artificial leather are shown in Tables 1 and 2 below.

[0073] Comparative Example 4 The surface fiber sheet weight is 150g / m2 A suede-like artificial leather 12 was obtained in the same manner as in Example 1, except that the material was stretched by 3% in each of the MD and CD directions instead of shrinking by thermal annealing. The manufacturing conditions and evaluation results of the obtained artificial leather are shown in Table 1 below.

[0074] Comparative Example 5 The surface fiber sheet weight is 20g / m 2 The weight ratio of the surface fiber sheet was set to 70:30 (main fiber:thermofusible fiber), and the base fabric was heated at 190°C for 5 minutes using a pin tenter dryer without slackening in the MD and CD directions, and no thermal annealing shrinkage was performed, to obtain suede-like artificial leather 13 in the same manner as in Example 1. The production conditions and evaluation results of the obtained artificial leather are shown in Table 1 below.

[0075] Comparative Example 6 The surface fiber sheet weight is 125g / m 2 The weight ratio of the surface fiber sheet was set to 97.5:2.5 (main fiber:thermofusible fiber), and the base fabric was heated at 190°C for 5 minutes using a pin tenter dryer without slackening in the MD and CD directions, and no thermal annealing shrinkage was performed, to obtain suede-like artificial leather 14 in the same manner as in Example 1. The production conditions and evaluation results of the obtained artificial leather are shown in Table 1 below.

[0076] Comparative Example 7 The heat-fusible fibers were sheath-core type heat-fusible fibers (Melty 4080 manufactured by Unitika Ltd.) made of polyethylene terephthalate copolymer with a melting point of 110°C, a single fiber fineness of 2.2 dtex, and a length of 5 mm. The surface fiber sheet had a basis weight of 139 g / m. 2 Suede-like artificial leather 15 was obtained in the same manner as in Example 1, except that heat treatment was performed at a temperature of 125°C while elongating the material by 3% in both the MD and CD directions instead of thermal annealing shrinkage. The production conditions and evaluation results of the obtained artificial leather are shown in Table 1 below.

[0077] [Comparative Example 8] The single fiber fineness of the heat-sealing fiber is 1.1 dtex, and the weight of the surface fiber sheet is 220 g / m 2The weight ratio of the surface fiber sheet was adjusted to 80:20 (main fiber:thermally fusible fiber), and the base fabric was heated at 130°C for 5 minutes using a pin tenter dryer without slackening in the MD or CD directions, resulting in a suede-like artificial leather 17, as in Example 1, except that no thermal annealing shrinkage was performed. No formation of molten resin was observed. The production conditions and evaluation results of the resulting artificial leather are shown in Table 1 below.

[0078] Comparative Example 9 The heat-fusible fiber was a sheath-core type heat-fusible fiber (Melty 4080 manufactured by Unitika Ltd., melting point 110°C) made of polyethylene terephthalate copolymer with a single fiber fineness of 2.2 dtex and a length of 5 mm, and the surface fiber sheet weight was 180 g / m 2 Suede-like artificial leather 18 was obtained in the same manner as in Example 1, except that the weight ratio of the surface fiber sheet was 85:15 (main fiber:heat-melt fiber), the weight ratio of the back fiber sheet was 96:4 (main fiber:heat-melt fiber), and the base fabric was heated at 80°C for 5 minutes using a pin tenter dryer without slackening in the MD or CD directions. No molten resin formation was observed. The production conditions and evaluation results of the obtained artificial leather are shown in Table 1 below.

[0079] [Table 1] [Industrial Applicability]

[0080] In the artificial leather of the present invention, the thermoplastic resin bonds the main fibers having a fineness of 0.01 dtex or more and 0.5 dtex or less together in a relaxed state of an entangled structure, and the aggregate size of the thermoplastic resin in the first surface fiber layer is 5000 μm in number average volume when measured by X-ray-CT. 3 More than 14000μm 3 and the volumetric number density is 1.1 × 10 12 pieces / m 3 Over 3.0 x 10 12 pieces / m 3Since the thickness is less than 100 μm, the artificial leather of the present invention has an excellent feel and high abrasion resistance. Furthermore, if the main fiber and thermoplastic fiber used are polyester-based fibers and do not contain an elastic polymer such as water-based polyurethane, the artificial leather of the present invention will have excellent recyclability. Because the artificial leather of the present invention has high stretchability, it is particularly suitable for stretching as a car ceiling material and can be suitably used as a car interior material. Furthermore, the artificial leather of the present invention can be suitably used not only as a car interior material, but also in fields such as seat coverings and interior materials for railway vehicles, aircraft, ships, etc., clothing, shoes, bags, smartphone cases, interior decoration, and furniture. [Explanation of symbols]

[0081] 1. Main fiber 2. Lump resin 3 Unmelted resin (heat-melting thread) 4. Sheath-core fibers 11 Fiber sheet 12 Scrims 13 Surface fiber layer (A) 14 Fiber layer (B) 21 Surface layer 22 scrim layer 23 Lining

Claims

1. An artificial leather comprising at least a surface fiber layer constituting a first surface, the artificial leather having the following characteristics: (1) The surface fiber layer is composed of at least one type of main fiber and a thermoplastic resin having a melting point that is 20°C or more lower than the melting point of the main fiber; (2) The fineness of the main fiber is 0.01 dtex or more and 0.5 dtex or less; (3) At least a part of the thermoplastic resin bonds the main fibers together; (4) When the first surface is measured by X-ray CT, the number average volume of the thermoplastic resin in the surface fiber layer is 5000 μm 3 14000 μm or more 3 The following is true: (5) The volume density of the thermoplastic resin in the surface fiber layer is 1.1 × 10 12 pieces / m 3 Above 3.0 x 10 12 pieces / m 3 and (6) The thermoplastic resin is a full-melt type heat-fusible fiber; Artificial leather having the above structure.

2. The artificial leather according to claim 1 , wherein the main fiber is a polyester fiber.

3. The artificial leather according to claim 1 or 2, wherein the thermoplastic resin is a polyester-based resin.

4. The artificial leather according to any one of claims 1 to 3, wherein the surface fiber layer is entangled with a scrim layer that is a woven fabric.

5. The artificial leather according to claim 4 , wherein the scrim layer is made of polyester-based resin fibers.

6. The artificial leather according to any one of claims 1 to 5, wherein when the surface is abraded at a pressing load of 12 kPa in accordance with JIS-L-1096 E method (Martindale method), the scrim is not exposed when the abrasion number is less than 50,000.

7. The artificial leather according to any one of claims 1 to 5, wherein when the surface is abraded at a pressure load of 12 kPa in accordance with JIS-L-1096 E method (Martindale method), the abrasion loss is 21 mg or less after 50,000 abrasion cycles.

8. The following steps: (1) Main fibers and heat-fusible fibers made of a thermoplastic resin having a melting point 20°C to 170°C lower than the melting point of the main fibers are mixed so that the weight ratio of the heat-fusible fibers is 3% to 25%, and then the mixture is entangled on a scrim layer by wet papermaking, and then a surface fiber web entangled with the scrim layer is formed by hydroentanglement treatment or needle punching; and (2) Relaxing the entangled structure of the obtained surface fiber web by thermal annealing shrinkage at a temperature equal to or higher than the melting point of the heat-fusible fibers and lower than the melting point of the main fibers to form a surface fiber layer; The method for producing an artificial leather according to any one of claims 1 to 7, comprising:

9. The method according to claim 8 , wherein the length of the subject fibers in the step (1) is 2.5 mm or more and 90 mm or less.

10. The method according to claim 8 or 9, wherein the fineness of the heat-fusible fibers in the step (1) is 0.5 dtex or more and 2.2 dtex or less.

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